US4239417A - Multi-purpose marine structure - Google Patents

Multi-purpose marine structure Download PDF

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Publication number
US4239417A
US4239417A US05/961,205 US96120578A US4239417A US 4239417 A US4239417 A US 4239417A US 96120578 A US96120578 A US 96120578A US 4239417 A US4239417 A US 4239417A
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US
United States
Prior art keywords
peripheral body
outer peripheral
structure according
section
inner section
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US05/961,205
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English (en)
Inventor
Arvid Slatten
Harald Bech
Olav Olsen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ING F SELMER AS
A S HOYER ELLEFSEN ING T FURUHOLMEN AS
Original Assignee
ING F SELMER AS
A S HOYER ELLEFSEN ING T FURUHOLMEN AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from NO774004A external-priority patent/NO774004L/no
Priority claimed from NO783000A external-priority patent/NO783000L/no
Application filed by ING F SELMER AS, A S HOYER ELLEFSEN ING T FURUHOLMEN AS filed Critical ING F SELMER AS
Application granted granted Critical
Publication of US4239417A publication Critical patent/US4239417A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
    • E02B17/02—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor placed by lowering the supporting construction to the bottom, e.g. with subsequent fixing thereto
    • E02B17/025—Reinforced concrete structures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
    • B63B21/24—Anchors
    • B63B21/26—Anchors securing to bed
    • B63B21/29—Anchors securing to bed by weight, e.g. flukeless weight anchors

Definitions

  • This invention relates to a moveable buoyant element designed for being submerged to the seabed and anchored there.
  • This buoyant element can be used for a number of different purposes or a combination of different purposes.
  • the buoyant element may be used in connection with an anchorage system for anchoring a supply ship in the vicinity of a marine platform.
  • said element may be used to protect seabed installations such as the well head and/or subsea completions.
  • the buoyant element or several such elements may be used for anchoring an oil boom to be placed around the platform in the event of an oil leakage, spill or blow-out.
  • the element according to this invention may be used for pulling a pipeline from a marine production/drilling platform to the element, or the element may be used as a foundation for a BOPS. Also the element or several such elements may be used in the installation phase to pull a marine platform into the desired position. Furthermore the element may be used as a manifold for connecting a number of different oil gas wells. In addition the element may be used to house processing equipment associated with the extraction and production of hydrocarbons. Moreover the element may be used as intermediate pulling station(s) for pipes/cables extending between a platform and, for example, a production element of a design corresponding to the element according to the present invention. This applies no matter whether the production element lies at the same level as or lower than the platform itself. It is also possible to use the anchor for anchoring a wave-operated electric power generating station and as an anchor/foundation for loading buoys.
  • the element may be used for oil storage or as an anchor for large floating structures such as floating drilling and/or production platforms for exploratory and/or production drilling for hydrocarbons in deep waters.
  • the element may be used as a riser base and can contain manifolds, valves etc.
  • the said versions of the element may be equipped with adaptors to receive diving bells and/or underwater craft.
  • the element When used in connection with oil/gas production the element can be filled with air and have atmospheric pressure. Or it can be filled with inert gas, or be filled with water at a pressure of 1 atmosphere. Alternatively the element can have full water pressure or a combination of the said conditions may be employed, depending upon which phase the operations have entered.
  • one or more stationary buoyant elements are used, resting on the seabed and located at a safe distance from a drilling and/or production platform.
  • the buoyant element consists of a tubular ring formed by a polygon or torus plus an approximately conical, hollow central section.
  • the said hollow ring element should be shaped as a torus formed by revolving a circular ring.
  • the torus may be formed by revolving a hollow polygon.
  • the said hollow ring element may be composed of preferably cylindrical sections assembled to form a polygonal element.
  • the approximately conical, hollow central section may be formed by a cone or a polygonal pyramid, preferably truncated.
  • the said approximately conical central section is fixed in the hollow, ring-shaped element in such a manner that the transition between cone and ring is continuous, without any sharp bends or changes of shape, the said cone and the ring-shaped element preferably forming a monolithic whole.
  • a preferred element is of concrete.
  • the greatest stresses to which the ring will be subjected will occur during submerging. Normally it will then have internal atmospheric pressure. Stress will become negligible after the concrete ring is filled with water.
  • the design of the concrete ring is determined largely in consideration of the heavy external stresses arising from water pressure during submerging. The chosen form is especially advantageous because essentially only membrane stresses will occur.
  • the element When used to protect wellheads the element may internally be divided into compartments to isolate each wellhead. It is an advantage if these walls have a curved design.
  • the underside of the element may be equipped with a skirt or ribs which are pressed down into the seabed.
  • the elements for the different purposes are very similar in design. However small modifications are necessary in order to satisfy, and depending upon, the various functions.
  • buoyant element according to the present invention A number of advantages are achieved by using the buoyant element according to the present invention. Among other things it is possible to reduce the total development cost for a field, whereby marginal fields attain more potential interest. Depending upon their shape and size, shallow reservoirs will become substantially cheaper to develop. By using only one large, centrally located platform and a number of multi-purpose elements according to this invention, it will be possible to reduce field development costs. Among other things it will be possible to commence production only a short time after the central platform is installed and the first satellite well(s) are connected up. This facilitates early start-up and consequently an early cash flow.
  • a further substantial advantage is that by using these buoyant elements as wellhead protection and installing the necessary oil/gas separating equipment inside the element, it becomes possible to separate oil and gas prior to transfer to the central platform, which reduces the wear/corrosion of pipe walls caused by the said mixture.
  • applications for the element can be divided into two main groups, the one group consisting of cases where the element is used as anchorage, either for anchoring a supply vessel or oil boom or for pulling the principal structure into the desired position during the installation phase.
  • the other group consists of use for covering wellheads or as a foundation for the BOP stack, or as a manifold element for connecting pipelines from the different wells.
  • FIG. 1 is a perspective drawing of a platform, a mooring buoy and a supply ship,
  • FIG. 3 shows a vertical section along line A--A in FIG. 2,
  • FIG. 4 is a perspective drawing of a gravity platform, anchorage elements and a supply ship in the process of laying an oil boom around the platform, the boom being held in position by means of the anchorage elements,
  • FIG. 5 shows the element used as wellhead protection, a gravity platform and the interlinking pipeline
  • FIG. 6 shows a horizontal plan of the element shown in FIG. 5
  • FIG. 7 shows on a larger scale detail A indicated inside the ring in FIG. 5,
  • FIG. 8 shows in perspective buoyant elements according to this invention used as manifold for the well and pipelines from other wells and/or as anchorage element for a semi-submerged floating platform
  • FIGS. 9-13 show various stages of building the anchorage element
  • FIGS. 14-16 show further details of the wellhead protection element of FIG. 5.
  • FIG. 1 shows in perspective a supply ship 1 anchored to a marine platform 2 by means of two wire ropes or hawsers 3 extending between the supply ship 1 stern and the platform 2.
  • the supply ship 1 is moored from the bow to a mooring buoy 4 via a forward wire rope or hawser 5 extending between the bows of the supply vessel 1 and the mooring buoy.
  • the mooring buoy 4 is securely anchored to the seabed by means of an anchorage element 7 resting on the seabed 6, a lower anchorline 8, an intervening buoy 9 and an upper anchorline 10.
  • the lower anchorline 8 is held taut preferably by the intervening buoy 9 having positive buoyancy. This reduces the wear on the lower anchorline 8 which in turn reduces inspection and maintenance frequency for this part.
  • the said intervening buoy 9 preferably lies approximately 20-30 meters below the sea surface 11.
  • FIG. 2 shows a horizontal plan of the anchorage element 7 according to the present invention.
  • This comprises a tubular, hollow ring element 12 plus a truncated cone 13 fitted centrally therein.
  • the ring element 12 consists of sixteen uniform and approximately cylindrical sections assembled to form a ring element 12 having sixteen sides.
  • the hollow space in each of the said sections is cylindrical in shape with a circular cross-section.
  • the ring element 12 is shaped as a torus formed by revolving a circular ring.
  • a torus-like ring element is preferred, composed of the above mentioned uniform, approximately cylindrical sections 14 as shown by the broken line in FIG. 3.
  • each section are given a form as shown in FIG. 3.
  • the external surface is formed by fourplane surfaces 15 combined with a dome-like calotte 6. This simplifies both formwork and casting, as conventional formwork units can be used for the plane surfaces, while preferably the dome-like calotte is cast without formwork.
  • the said four plane external surfaces 15 are so arranged relative to each other that two of the surfaces are parallel and vertical, while two form a V-shaped lower edge or rim 17. To a certain extent this edge 17 will act as an anchoring skirt.
  • the ring element may be provided with a skirt (not shown) or rib extending around the ring element which, together with or instead of the said edge, is designed to provide adequate anchorage for the ring element.
  • the angle between the surfaces which form the said V is chosen so that the walls in the said "conical" element form a continuous, rectilinear extension.
  • the anchorage element is provided with a ballast system for filling/draining ballast water in the ring element 12 if desired.
  • FIG. 4 is a perspective drawing of supply ship 1 in the process of laying an oil boom 18 around a marine platform 2 standing on the seabed.
  • an anchoring system is used which largely corresponds to the anchoring system described in connection with FIGS. 1-3.
  • This anchoring system comprises an anchorage element 7, a lower anchorline 8, an intervening buoy 9, an upper anchorline 10 and a buoyancy element/anchoring buoy 4.
  • the number of anchorage units in the system is determined by the length of the oil boom 18.
  • Said anchorage units are placed in advance in the desired positions around the platform 2.
  • Said anchoring system can function also as an anchoring system for anchoring supply ships, corresponding to the system described in connection with the applications shown in FIGS. 1-3.
  • the said anchorage elements 7 can to advantage be installed prior to positioning the platform 2, whereby said anchorage elements 7 can be used for accurate positioning of the field, possibly above previously drilled and completed wells 19.
  • FIG. 5 shows the element 7 used as protective casing fitted over wellheads 19 to protect them.
  • Said satellite well 19 is linked with production platform 2 by pipelines 20.
  • the ring element 12 can be partly or fully air-filled.
  • the element 7 is provided with adaptors for receiving diving bells/underwater craft 21.
  • the ring element 12 contains any equipment that may be required in connection with wellhead 19 maintenance/repairs.
  • the element 7 has a slightly modified form, the walls of the truncated cone 13 being more vertical than shown in the previous drawings.
  • the horizontal section 22 of the truncated cone/pyramid 13 is larger.
  • Said area 22 is provided with a number of closable openings 23. These openings 23 are provided to facilitate drilling/maintenance of the wells 19.
  • FIG. 6 shows a horizontal plan of the element shown in FIG. 5.
  • FIG. 7 shows a detail on a larger scale. Details are denoted "Detail A" in FIG. 5. More specifically FIG. 7 shows two stages of pulling the pipeline 20 from the platform 2 to the element 7. The one stage is immediately before the pipeline 20 is pulled through the plane surface 15 of the ring element 12, while the other stage is after the pipeline 20 has been pulled through a bushing 24 provided in the wall 15.
  • the bushing 23 is provided with conventional sealing and fastening means (not shown) for sealing and fastening the pipe 20 to the bushing 24, as well as a so-called bell mouth 25.
  • the pipeline 20 is pulled from the platform 2 toward the element 7 by means of wires 26 and one or more winches, tackle etc. provided in the ring element 12. Said winches, tackle etc.
  • the diameter of the pipe 20 may be so large that the cross-sectional area is sufficient to house a number of separate oil/gas transfer pipelines, and possibly to house a transport system to carry personnel from the platform 2 to the ring element 12 or vice versa.
  • Such a large pipe could also be designed to contain other units and equipment besides serving other functions, without departing from the idea of the invention.
  • FIG. 8 is a perspective drawing of the elements 7 according to the invention used as manifold for pipelines 20 from various satellite wells 19 and as anchorage elements for anchoring a semi-submersible platform. Moreover FIG. 8 shows the element 7 used as wellhead 19 protection.
  • the drawing shows a floating platform 27 anchored to the seabed 6 by means of anchorlines 28. These anchorlines are in turn anchored to the seabed 6 by means of anchorage elements 7.
  • the anchorage element also forms a protective casing fitted over wellheads 19.
  • the said anchorage elements must necessarily consist of separate anchorage elements, in contrast to the system shown in FIG. 8. Oil is transferred from the satellite wells 19 through pipelines 29 to a manifold element 20, and from there on to the floating platform 27 through risers 31.
  • the element 7 can be put to combined use as wellhead protection and manifold station.
  • the wellheads 19 can either be arranged inside the truncated cone/pyramid 13 or may be inside the ring element 12. If the wells 19 are inside the truncated cone/pyramid 13, they are under full water pressure. On the other hand, if the wells 19 terminate in the ring element 12, they can be under air or alternatively atmospheric pressure. In the event that the wells 19 terminate inside the truncated cone/pyramid 13, any manifold could be in the ring element 12.
  • the BOP stack can either be fitted on top of and outside the ring element 12 or it can be fitted inside the ring element 12.
  • FIGS. 9-13 show various stages of a proposed procedure for building and installing the element according to this invention.
  • the torus containing the manifold and wellheads may be adapted for various applications.
  • the openings B in the top of the torus may be so large that the whole BOP stack passes through the opening and is installed on a concrete slab in the bottom.
  • the Xmas tree C is installed in the conventional manner and a large concrete/steel cover is fitted on top of the opening in the torus.
  • a cylindrical wall A cast in steel or concrete can be fitted around the Xmas tree to separate it from the remainder of the cavity. This wall need not extend fully to the bottom, but may be suspended from the roof of the cavity as shown in FIG. 15.
  • the cavity can then be filled with water up to slightly above the lower section of this cylinder A. Any leaking gas or oil would thereby be prevented from penetrating into the other section of the cavity. For repairs it would in that event be necessary to dive under the cylinder edge to gain access to the Xmas tree C and the leakage.
  • the cavity inside the cylinder could then be filled with non-explosive gas. It would also be possible to operate with differing pressures inside the cylinder A relative to the remainder of the cavity. This would facilitate relatively early registration of any excess pressure building up inside the cylinder A due to leakage from the Xmas tree.
  • the cavity can be divided into two or more sections by building walls D. These walls can be arched to be better able to withstand pressure and to lessen the stresses on the circular external walls.
  • Upright walls D may also be used.
  • Such arched or upright walls D of concrete or steel may also be fitted to isolate each well installation.
  • the structure may also be installed with so-called J tubes E whereby oil/gas pipelines can be pulled to other, smaller satellite installations, but where at the same time manifold F will be used in the described structure.
  • One or more structures G should be installed for protection of personnel.
  • the drawing shows a workplace/accommodation, an operating chamber and a transfer chamber to an underwater vessel or diving bell.
  • These chambers G may be built of either steel or reinforced concrete.
  • the cylinder/torus can contain separators and processing equipment too.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Ocean & Marine Engineering (AREA)
  • Earth Drilling (AREA)
US05/961,205 1977-11-23 1978-11-16 Multi-purpose marine structure Expired - Lifetime US4239417A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
NO774004 1977-11-23
NO774004A NO774004L (no) 1977-11-23 1977-11-23 Forankringssystem.
NO783000A NO783000L (no) 1978-09-01 1978-09-01 Marin flerfunksjonskonstruksjon.
NO783000 1978-09-01

Publications (1)

Publication Number Publication Date
US4239417A true US4239417A (en) 1980-12-16

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ID=26647650

Family Applications (1)

Application Number Title Priority Date Filing Date
US05/961,205 Expired - Lifetime US4239417A (en) 1977-11-23 1978-11-16 Multi-purpose marine structure

Country Status (6)

Country Link
US (1) US4239417A (fr)
AU (1) AU523326B2 (fr)
CA (1) CA1093324A (fr)
GB (1) GB2009824B (fr)
IN (1) IN150477B (fr)
IT (1) IT1100357B (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6571878B2 (en) * 1999-09-16 2003-06-03 Shell Oil Company Smooth buoyancy system for reducing vortex induced vibration in subsea systems
US6761508B1 (en) 1999-04-21 2004-07-13 Ope, Inc. Satellite separator platform(SSP)
WO2006038018A1 (fr) * 2004-10-08 2006-04-13 Electromagnetic Geoservices As Degradation regulee d'ancres en beton non renforce
US20080302535A1 (en) * 2007-06-08 2008-12-11 David Barnes Subsea Intervention Riser System
US20130133563A1 (en) * 2011-11-26 2013-05-30 Stephan Vincent Kroecker Mono Semi-Submersible Platform

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO167098C (no) * 1988-11-16 1991-10-02 Aker Eng As Modulaer beskyttelsesstruktur for undervannsinstallasjoner.
GB2234002A (en) * 1989-06-16 1991-01-23 Northern Ocean Services Ltd Protective structure for sub-sea well heads or Xmas trees

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3385464A (en) * 1965-04-20 1968-05-28 Equipements D Entpr S Sa Soc E Immersible tank with ballast means for its transport and immersion
US3703207A (en) * 1970-07-29 1972-11-21 Deep Oil Technology Inc Subsea bunker construction
US3835654A (en) * 1971-09-09 1974-09-17 Campenon Bernard Europe Submersible tanks containing oil or similar liquids
US4065935A (en) * 1975-07-18 1978-01-03 Taylor Woodrow Construction Limited Articulated joints for deep water installations

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3385464A (en) * 1965-04-20 1968-05-28 Equipements D Entpr S Sa Soc E Immersible tank with ballast means for its transport and immersion
US3703207A (en) * 1970-07-29 1972-11-21 Deep Oil Technology Inc Subsea bunker construction
US3835654A (en) * 1971-09-09 1974-09-17 Campenon Bernard Europe Submersible tanks containing oil or similar liquids
US4065935A (en) * 1975-07-18 1978-01-03 Taylor Woodrow Construction Limited Articulated joints for deep water installations

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6761508B1 (en) 1999-04-21 2004-07-13 Ope, Inc. Satellite separator platform(SSP)
US6571878B2 (en) * 1999-09-16 2003-06-03 Shell Oil Company Smooth buoyancy system for reducing vortex induced vibration in subsea systems
WO2006038018A1 (fr) * 2004-10-08 2006-04-13 Electromagnetic Geoservices As Degradation regulee d'ancres en beton non renforce
US20090007834A1 (en) * 2004-10-08 2009-01-08 Svein Ellingsrud Controlled Deterioration of Non-Reinforced Concrete Anchors
US8075685B2 (en) 2004-10-08 2011-12-13 Electromagnetic Geoservices As Controlled deterioration of non-reinforced concrete anchors
US20080302535A1 (en) * 2007-06-08 2008-12-11 David Barnes Subsea Intervention Riser System
US20130133563A1 (en) * 2011-11-26 2013-05-30 Stephan Vincent Kroecker Mono Semi-Submersible Platform

Also Published As

Publication number Publication date
GB2009824A (en) 1979-06-20
AU523326B2 (en) 1982-07-22
GB2009824B (en) 1982-04-28
AU4178678A (en) 1979-05-31
IT1100357B (it) 1985-09-28
IN150477B (fr) 1982-10-23
IT7830100A0 (it) 1978-11-23
CA1093324A (fr) 1981-01-13

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